Chemical mechanical machining and surface finishing

ABSTRACT

The invention described herein discloses a chemical mechanical machining and surface finishing process. A conversion coating is formed on the surface of a workpiece and is removed via relative motion with a tool, thereby exposing the workpiece to further reaction with the active chemistry. Low mechanical forces are used such that the plastic deformation, shear strength, tensile strength and/or thermal degradation temperature of the workpiece are not exceeded. Since the chemical mechanical machining and surface finishing process requires little force and/or speed of contact to remove the conversion coating, the equipment&#39;s mass, complexity and cost can be significantly reduced, while simultaneously increasing machining precision and accuracy. The present invention lends itself to a very controlled rate of metal removal, and can simply surface finish the workpiece, or if desired, can surface finish the workpiece simultaneously with the shaping and/or sizing process.

BACKGROUND OF THE INVENTION

[0001] Conventional mechanical machining is a highly aggressive process.No matter how much care and vigilance is taken, this process almostalways results in metallurgical damage, if even only at the microscopiclevel, due to the application of highly concentrated forces andconcomitant localized high temperature spikes. Such damage can includemicrocracks, the introduction of stress raisers, oxidation, phase changeand a reduction in beneficial residual compressive stress andmicrohardness. The grinding process, for example, can generatesufficient heat to temper the surface of a hardened workpiece, oftenreferred to as grinding burn, thus reducing the workpiece's wear andcontact fatigue properties. In addition, conventional mechanicalmachining always produces burrs and machine lines. These residual burrsand machine lines are stress raisers that must be removed from criticalsurfaces in order to reduce wear, friction, operating temperature,scuffing, contact fatigue failure (pitting), and/or various dynamicfatigue failures such as bending, torsional and axial fatigue.

[0002] Besides metallurgical damage to the workpiece, conventionalmachining operations have an inherent limitation in producing workpieceswith extremely high dimensional precision and accuracy. As mentionedpreviously, mechanical machining involves the aggressive shearing ofmetal from a workpiece by a tool that moves with a high speed and/orhigh force. Thus, tool wear is intrinsic to the process. Maintainingworkpiece-to-workpiece dimensional precision and accuracy, however,relies on the ability to maintain dimensional stability of the tool.Tool wear becomes extremely problematic as the hardness of the workpieceincreases to 40 HRC and greater. Gears and bearings, for example, aretypically hardened to 55-65 HRC or higher.

[0003] The machine that guides the cutting tool has its own inherent setof limitations that inhibit high precision and accuracy. Somelimitations of the mechanical devices moving the tool include geometricerrors, feed rate errors, drive wear, vibration, and hysteresis, to namea few. The machines are usually massive in size so as to maintain therequired rigidity to accurately apply the high forces that are necessaryto remove metal especially from hard workpieces. Significant thermaldistortions and structural deflections caused by the cutting load canalso be problematic, especially for delicate workpieces.

[0004] In addition to machine lines, the forces applied to effect theaggressive cutting action of the tool also generate vibrations that leadto chatter. Chatter and machine lines are typically reduced by amultiple step process. For example, in the case of a high quality gear,the gear must be ground, and then honed to reduce the chatter andmachine lines generated by machining. In the absence of extreme care,the grinding and honing processes can cause severe metallurgical damageto the critical contact surface of workpieces. Workpiece quality canonly be ensured by costly 100% inspection.

[0005] The importance of a smooth surface finish cannot beoveremphasized, particularly for metal-to-metal contact workpieces suchas gears, bearings, splines, crankshafts, and camshafts, to name a few,that often have machine or grind lines or other surface imperfectionsthat are very difficult to remove. For these workpieces, the asperitiescan increase friction, noise, vibration, wear, scuffing, pitting,spalling, operating temperature, and impair lubricity. For load-bearingarticles, machine lines on the surface can provide an initiation pointfor fatigue fractures in workpieces that are subjected to fluctuatingstresses and strains. As a result, there is a serious need to removestress raisers caused by conventional machine lines.

[0006] One method of surface finishing such workpieces is to machine thesurfaces by conventional multi-step, successively finer grinding, honingand lapping. Attaining a ground surface with a <2 microinch R_(a)requires time, multiple steps and state of the art technology. A complexsurface geometry calls for expensive and highly sophisticated machinery,expensive tooling and time consuming maintenance. In addition to thecost, this process produces directional lines and the potential fortempering and microcracks that damage the integrity of the heat treatedsurface. As previously discussed, a quality workpiece requires costly100% inspection of the ground and hardened surface with a technique suchas nital etching. Another shortcoming of this approach is thepossibility of abrasive particles being impregnated into the surfaceresulting in stress raisers, lubricant debris and/or wear.

SUMMARY OF THE INVENTION

[0007] The invention described herein discloses a chemical mechanicalmachining and surface finishing process. An active chemistry is reactedwith the surface of a workpiece so that a soft conversion coating isformed on the surface of a workpiece. The conversion coating isinsoluble in the active chemistry in that it protects the basis metal ofthe workpiece from further chemical reaction with the active chemistry.The conversion coating is removed from the workpiece via relative motionwith a contact tool, thereby exposing fresh metal for further reactionwith the active chemistry, which allows the conversion coating to reformon the workpiece.

[0008] Low mechanical forces are used to remove the conversion coatingfrom the workpiece, wherein the plastic deformation, shear strength,tensile strength and/or thermal degradation temperature of the basismetal of the workpiece are not exceeded. Thus, this chemical mechanicalprocess eliminates the potential for tempering, microcracking, stressraisers and other metallurgical damage associated with conventionalmachining. Since the chemical mechanical machining and surface finishingprocess requires little force and/or speed of contact to remove theconversion coating, the equipment's mass, complexity and cost can besignificantly reduced compared to conventional machining equipment whilemachining precision and accuracy can be increased. Tool wear is alsominimal or eliminated due to the ability to operate at reduced cuttingforces, speeds and operating temperatures. These reductions allow thetool to be fashioned from non-abrasive or slightly abrasive materialsthat are softer than the basis metal of the workpiece. The tool can berigid or flexible such that it conforms to the surface of the workpiece.

[0009] In certain applications, machining equipment can be completelyeliminated, wherein mating workpieces in relative motion and load act asthe tools for the removal of the conversion coatings from their opposingcontact surfaces. The present invention lends itself to a verycontrolled rate of metal removal, and can just surface finish theworkpiece, or if desired, surface finish the workpiece simultaneouslywith the shaping and/or sizing of the workpiece. As used herein,“surface finishing” means to remove metal from the surface of aworkpiece to reduce roughness, waviness, lays and flaws. “Sizing” meansto uniformly remove metal from the surface of a workpiece to bring it toits proper dimension. “Shaping” means to differentially remove metalfrom a workpiece to bring it to its proper geometry. “Shaping” includesdrilling, sawing, boring, cutting, milling, turning, grinding, planing,and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 shows an example of a Falex Corporation FLC LubricityTester as used in examples 2 and 3.

[0011]FIG. 2 shows another example of a Falex Corporation FLC LubricityTester as used in examples 4 and 5.

DETAILED DESCRIPTION OF THE INVENTION

[0012] In lieu of traditional cooling lubricants, the chemicalmechanical machining and surface finishing process disclosed herein useswater-based or organic-based active chemistry capable of reacting withthe surface of a metal workpiece, common metals being iron, titanium,nickel, chromium, cobalt, tungsten, uranium, and alloys thereof. Theactive chemistry is first introduced into the shaping, sizing and/orsurface finishing machine so as to react with the basis metal of theworkpiece to form a soft conversion coating. The conversion coating isinsoluble in the active chemistry in that it protects the basis metal ofthe workpiece from further chemical reaction with the active chemistry.The conversion coating can comprise, for example, metal oxides, metalphosphates, metal oxalates, metal sulfates, metal sulfamates, or metalchromates.

[0013] The formation of the conversion coating is followed byappropriate tooling contact having a relative motion between the tooland the workpiece. The relative motion can be produced by movement ofthe tool across a stationary work piece, by movement of the workpieceacross a stationary tool, or by movement of both the tool and theworkpiece. The conversion coating is rubbed off by the tool, therebyexposing fresh metal on the workpiece, allowing for the re-formation ofthe conversion coating on the exposed metal. The metal removal rate isproportional to the rate of reaction of the active chemistry with themetal to form the conversion coating. This reaction rate can beincreased by raising the temperature and by using chemical accelerants.As the reaction rate increases, the metal removal rate will becontrolled by the rate of conversion coating removal. This process ofrubbing and re-formation is repeated until such time as the desiredsurface finishing and/or shaping and/or sizing is achieved. Nometallurgical damage occurs. The machining tool requires very littleforce to remove the conversion coating, and thus the machine's mass,complexity and cost can be significantly reduced as compared toconventional machining while machining precision and accuracy can beincreased.

[0014] In the embodiments of the present invention, the relative motionand contact force of the tool and workpiece is less than the plasticdeformation, shear strength and/or tensile strength of the workpiecesuch that thermal degradation temperatures are not produced on theworkpiece. In some embodiments, the contact between the tool and theworkpiece causes metal to be removed from the workpiece at a theoreticalresolution of 1.0 microinch. Because of the small force applied to theworkpiece from the tool, tool wear is minimized and/or eliminated. Thischemical mechanical process lends itself to a very controlled rate ofmetal removal, and can surface finish the workpiece simultaneously withthe shaping and/or sizing process.

[0015] When using this chemical mechanical machining and surfacefinishing process, a conversion coating is formed on the surface of theworkpiece that is softer than the basis metal of the workpiece. Anyactive chemistry that can form such a chemical conversion coating on thesurface of the workpiece is within the contemplation of the invention.Although the properties exhibited by the conversion coating produced onthe basis metal are important to the successful practice of the presentprocess, the formulation of the active chemistry is not. One suchconversion coating is described in U.S. Pat. No. 4,818,333, assigned toREM Chemicals, Inc., the contents of which are herein incorporated byreference.

[0016] The active chemistry preferably is capable of quickly andeffectively producing, under the conditions of operation, a softconversion coating of the basis metal. The conversion coating mustfurther be substantially insoluble in the active chemistry and protectthe basis metal from further reaction so as to ensure that metal removaloccurs primarily by rubbing and reformation rather than by dissolution.

[0017] The active chemistry can also include activators, accelerators,oxidizing agents and, in some instances, inhibitors and/or a wettingagents. It should be noted that the amount of the added ingredients mayexceed solubility limits without adverse effect. The presence of aninsoluble fraction may be beneficial from the standpoint of maintaininga supply of active ingredients for replenishment of the active chemistryduring the course of operations.

[0018] In more specific terms, depending upon the metal substrateinvolved, the active chemistry will typically comprise phosphate saltsor phosphoric acid, oxalate salts or oxalic acid, sulfamate salts orsulfamic acid, sulfate salts or sulfuric acid, chromates or chromicacid, or mixtures thereof. In addition, known activators or acceleratorsmay be added to the active chemistry such as, but not limited to,selenium, zinc, copper, manganese, magnesium and iron phosphates, aswell as inorganic and organic oxidizers, such as but not limited topersulfates, peroxides, meta-nitrobenzenes, chlorates, chlorites,nitrates and nitrites.

[0019] The active chemistry used in this invention can be diluted ordispersed. The diluent or dispersant will most commonly be water, butcan also be a material other than water such as, but not limited to,paraffinic oil, organic liquid, silicone oil, synthetic oil, other oils,greases, or lubricants. It is also anticipated that under certainconditions it might be preferable to create the conversion coating withhighly concentrated acids such as sulfuric acid, methane sulfonic acidor phosphoric acid where water is a very minor component. Furthermore,an oil or lubricant can be used as the diluent or dispersant ifdesirable. This is desired when, for example, sulfuric acid is used witha mineral oil. Sulfuric acid is not appreciably soluble in mineral oils,but the mineral oil will act as a dispersant, as the sulfuric acid willbe dispersed, instead of dissolved, throughout the mineral oil.

[0020] Any tool that can remove the soft conversion coating, previouslydescribed, to expose fresh metal without exceeding the plasticdeformation, shear strength and/or tensile strength of the workpiecesuch that thermal degradation temperatures are not produced on theworkpiece is within the contemplation of the invention. Although theproperties of the tool are important to the successful practice ofremoving the conversion coating, the tool design is not. In some cases,the tool can be the mating surface of the workpiece or a facsimilethereof. For example, the workpiece can comprise a gear, and the toolcan comprise a mating gear or facsimile thereof. In another example, theworkpiece can comprise a bearing race, and the tool can comprise aplurality of mating bearing balls or rollers or facsimile thereof.

[0021] In accordance with the present invention, the tool can be eitherrigid or flexible. For example, if the workpiece is the root fillet of agear, the tool can be a rigid, slightly abrasive cylinder sized suchthat it will contact all desired recessed areas to remove machine and/orgrind lines and/or shot peening pattern. In another example, if theworkpiece is the interior surface of a pipe or tube, a flexible and/orexpandable tool that conforms to the workpiece can be used to improvethe surface finish by removing forming lines or welding seams.

[0022] In one embodiment, the tool is not reactive with the activechemistry, in that the chemically induced conversion coating is notformed on the tool. Contemplated non-reactive materials that the toolcan be made from are wood, paper, cloth, ceramic, plastic, polymer,elastomer, and metal, but any material that is not reactive with theactive chemistry can be used. For instance, if the workpiece is a gear,the tool may be a non-reactive mating gear designed to impart therequired shaping and/or surface finishing properties while running inmesh with the reactive workpiece.

[0023] There are a number of advantages of this chemical mechanicalmachining and surface finishing process. This process achieves awell-controlled metal removal rate capable of producing workpieces withhigh dimensional precision and accuracy. Metal can be removed with aresolution of approximately 1.0 microinch. This process also has theability to simultaneously shape and/or size and/or surface finish,thereby reducing the gross number of processing steps. Since less forceneeds to be imparted to effect metal removal, a smaller, less complexand less expensive machine can be used to guide the tool. Tool speed isalso much lower than that required in conventional machining, and toolcosts and wear are significantly reduced.

[0024] Furthermore, much larger machining surface areas can be shapedand/or sized and/or surface finished at one time. This process alsovirtually eliminates burrs, machine lines, chatter, plastic deformation,and other surface deformities on the workpiece. A further advantage ofthe present process is a cool and burn-free machining process thatcauses little or no stress or metallurgical damage such as oxidation,phase change, stress raisers, and hardness changes. This process isusually carried out at or below the thermal degradation temperature ofthe metal. The low temperature also can help to eliminate the thermaldeformation of delicate workpieces. In addition, structural deflectionsare minimized under the reduced tool pressure, which is especiallyimportant on delicate workpieces, minimizing and/or eliminatingstructural distortion and like deformities. Finally, the precision andaccuracy of the machining process is tremendously improved.

[0025] In another embodiment of the present invention, in-situ shapingand/or sizing and/or surface finishing of metal-to-metal contactsurfaces can be accomplished. This is done by adding active chemistry,with or without a fine abrasive, to the assembled apparatus so that aconversion coating is formed on the individual reactive metal surfacesof both the workpiece and the tool. Initially the apparatus can beoperated under low load, which can be gradually increased to full loadconditions. The conversion coating will be removed only at the criticalcontact surface where the rubbing, rolling, sliding, and the like occurto expose fresh metal for further reaction. Chemical mechanicalmachining and surface finishing will occur only at the critical contactsurfaces to remove asperities that ultimately results in a line-free ornearly line-free surface. The process can be continued, if desired, toattain a superfinished surface and/or final shaping and/or sizing ofmating workpieces to their ideal geometry. Thus, each mating surfacewill have an ideal matching contact surface area. The in-situ processcan correct minor dimensional or geometrical errors in the matingcomponents with highly controlled precision by adjusting the activechemistry characteristics, processing time and temperature, contactloading and contact speed.

[0026] In-situ surface finishing or superfinishing also has otheradvantages, such as making it possible to finish all of the criticalcontact surfaces of an entire assembly, such as a transmission, thatsignificantly reduces the cost of finishing each individual workpiece.Once a process is optimized, the surface finishing is extremelyreproducible, and can be accomplished easily in a factory environment,thus eliminating the need for 100% final inspection. The process can becarried out in or outside of the housing, and can concurrently finalshape and/or size assembled mechanisms by removing minordimensional/geometrical errors in the mating components. In gear andbearing applications, for example, this process reduces break-inperiods, wear, scuffing, operating temperatures, friction, vibration andnoise.

[0027] One embodiment of this in-situ process is two mating gears. Theactive chemistry can be introduced onto a first mating gear, forming aconversion coating on the first mating gear, while simultaneouslyforming a conversion coating on the second mating gear. The two matinggears are contacted with a relative motion therebetween thatsimultaneously removes the conversion coatings from the two gears. Thus,both gears are exposed to further reaction with the active chemistrysuch that the conversion coating is allowed to be re-formed and removedon the gears, until a desired surface property, such as surfacefinishing, shaping, sizing or combination thereof, of both gears isreached. In one embodiment, the gears are located within a transmissionor gearbox, wherein the contact between the gears occurs duringoperation of the transmission or gearbox.

[0028] In another embodiment, a bearing race and a plurality of matingrolling elements are provided. The active chemistry is introduced ontothe bearing race, simultaneously forming a conversion coating on thebearing race and the rolling elements. The bearing race and matingrolling elements are contacted with a relative motion therebetween thatsimultaneously removes the conversion coatings from the bearing race andthe mating rolling elements. Thus, both the bearing race and the matingrolling elements are exposed to further reaction with the activechemistry such that the conversion coating is allowed to be re-formedand removed, until a desired surface property, such as surfacefinishing, shaping, sizing or combination thereof, of the bearing raceand mating rolling elements is reached.

EXAMPLE 1 In-Situ Surface Finishing

[0029] Two similar SAE 4140 carbon steel, 43-45 HRC, with nominal sizeof 3 inches by 1 inch by ½ inch were used as test samples. One ½ inch by3-inch surface of each test sample was traditionally mechanicallypolished with 180 grit silicon carbide wet/dry paper in the longitudinaldirection. The starting R_(a) and R_(max) of Coupon 1 were 10.0 μin. and98.4 μin., respectively. The starting R_(a) and R_(max) of Coupon 2 were17.6 μin. and 167 μin., respectively.

[0030] Coupon 2 was placed in a solution of 60 g/L oxalic acid and 20g/L sodium metanitrobenzene sulfonate with its traditionallymechanically polished surface facing up. The traditionally mechanicallypolished surface of Coupon 1 was then placed in contact perpendicular tothe traditionally mechanically polished surface of Coupon 2. Coupon 2was held in a fixed position, and Coupon 1 was moved by hand in aback-and-forth and circular motion to simulate sliding motion ofcritical contact surfaces. Only very light pressure was applied. Thiswas continued for approximately 10 minutes. The final R_(a) and R_(max)of Coupon 1 at the metal-to-metal contact surface were 1.71 μin. and27.6 μin., respectively. The final R_(a) and R_(max) of Coupon 2 at themetal-to-metal contact surface were 1.95 μin. and 45.4 μin.,respectively.

[0031] Example 1 shows that two mating workpieces fabricated from ahardened metal can be surface finished and even superfinished, and/orsized and/or shaped by wetting the surfaces with an appropriate activechemistry while lightly rubbing them together. No abrasives, hightemperatures or high pressures are needed in this embodiment of theinvention. The surface is shaped and/or sized and/or surface finishedonly where there is metal-to-metal contact.

[0032] When two or more gears are in mesh in a gearbox, their flanks canbe shaped and/or surface finished in a similar fashion to thatdemonstrated in Example 1. This could be accomplished, for example, byturning the input shaft of the gearbox while applying a light load tothe output shaft. The contact regions of the gear teeth would be wettedwith the appropriate active chemistry either by continually flowingfresh active chemistry over the gear faces or by adding the activechemistry as a batch to the gearbox where the gears would be wetted withthe active chemistry. With time the contact surfaces of the teeth willbecome smoother and the tooth profile will be shaped to the ideal geargeometry.

[0033] Similarly bearings can be shaped, sized and/or surface finishedby the addition of active chemistry to the workpieces while runningunder very light loading. No metallurgical damage can occur as inconventional machining that uses abrasives or forces that generate highlocalized temperatures resulting in stress raisers or tempering leadingto premature workpiece failure from friction, wear, scuffing, contactfatigue and dynamic fatigue.

[0034] The present invention is not limited to bearings or gears, butcan be applied to any hard metal-to-metal contact that would benefitfrom surface finishing and/or sizing and/or shaping. The ability toshape and/or size and/or surface finish in one step increases themanufacturing efficiency for a variety of workpieces.

EXAMPLE 2 Traditional Mechanical Machining Baseline with SlightlyAbrasive Tool

[0035] A Falex Corporation FLC Lubricity Test Ring, SAE 52100 steel, HRC57-63, (part #001-502-001P), is traditionally mechanically machinedusing a slightly abrasive (600 grit) silicon carbide wet/dry paper andSAE 30 weight detergent free motor oil as a cooling lubricant.

[0036] A Falex Corporation FLC Lubricity Tester is used to rotate thering at a set RPM while a hard plastic mold (Facsimile®) of the outerring surface holds a piece of 600 grit silicon carbide wet/dry paperagainst it. The Falex supplied 0-150 foot-pound Sears Craftsman torquewrench with gravity acting on it is the only load applied to thetraditional mechanical grinding process. The ring is partially submergedin a reservoir of SAE 30 weight detergent free motor oil throughout thetest. FIG. 1 illustrates the test apparatus.

[0037] The test ring is cleaned, dried and weighed before and afterprocessing on an analytical balance to determine metal removal.

[0038] The test ring has a weight of 22.0951 grams before processing.After a period of 1.0 hour of processing at 460 RPM the weight is22.0934 grams. This is a loss of 0.0017 grams per hour that calculatesto an 8.9 μin. change in dimension.

EXAMPLE 3 Chemical Mechanical Machining with Slightly Abrasive Tool

[0039] A Falex Corporation FLC Lubricity Test Ring, SAE 52100 steel, HRC57-63, (part #001-502-001P), is chemically mechanically machined using aslightly abrasive (600 grit) silicon carbide wet/dry paper and FERROMIL®FML-575 IFP which is maintained at 6.25% by volume as the activechemistry to produce the conversion coating.

[0040] A Falex Corporation FLC Lubricity Tester is used to rotate thering at a set RPM while a hard plastic mold (Facsimile®) of the outerring surface holds a piece of 600 grit Silicon Carbide wet/dry paperagainst it. The Falex supplied 0-150 foot-pound Sears Craftsman torquewrench with gravity acting on it is the only load applied to thechemical mechanical process. The ring is partially submerged inFERROMIL® FML-575 IFP that is flowing through the reservoir at 6.5milliliter/minute at ambient room temperature. See FIG. 1 for image oftest apparatus.

[0041] The test ring is cleaned, dried and weighed before and afterprocessing on an analytical balance to determine metal removal.

[0042] The test ring has a weight of 22.1827 grams before processing.After a period of 1.0 hour of processing at 460 RPM the weight is22.1550 grams. This is a loss of 0.0277 grams per hour that calculatesto a 145.6 μin. change in dimension. These results show that the metalremoval rate is 16 times that of Example 2.

[0043] Examples 2 and 3 demonstrate that chemical mechanical machiningon hard workpieces increases the rate of metal removal dramatically.Therefore, it is possible to shape and/or size and/or surface finishhardened metal workpieces using a slightly abrasive tool in conjunctionwith active chemistry. The hardness of the workpiece is inconsequentialfor as long as the active chemistry reacts with the surface. In fact,the rate of metal removal stays approximately the same no matter howhigh the hardness of the metal. In sharp contrast, in conventionalmachining (e.g., grinding, honing, polishing, etc.) as the workpiece'shardness increases to 60 HRC and higher, tool wear increases while metalremoval rates decrease.

[0044] The embodiment of the invention of Examples 2 and 3 demonstratesthat it is possible to shape and/or size and/or surface finish extremelyhard metal surfaces using a slightly abrasive tool. This could be used,for example, to shape and/or surface finish the tooth profile of a gear.In this case, for example, a small rotating and/or vibrating tool with alight abrasive would be placed in contact with the gear flank of a gearthat is continually wetted with an appropriate active chemistry. Thiswould remove the machine and/or grind lines and be used to shape thetooth to the ideal gear geometry. This would significantly increase theservice life of gears that experience bending fatigue, scuffing, andother failures while reducing gear noise and allowing for increasedoperating power densities.

[0045] The present invention is not limited to gears, but can be appliedto any hard metal surface that would benefit from shaping and/or sizingand/or surface finishing. The ability to shape and surface finish in onestep will increase the manufacturing efficiency of a variety ofworkpieces.

EXAMPLE 4 Traditional Mechanical Grinding Baseline with Non-AbrasivePlastic Tool

[0046] A Falex Corporation FLC Lubricity Test Ring, SAE 4620 steel, HRC58-63, (part #S-25), is finished using REM® FBC-50 (soap mixture toprevent flash rusting and thermal degradation of the tool, but notcapable of producing a conversion coating).

[0047] A Falex Corporation FLC Lubricity Tester is used to rotate thering at a set RPM while a piece of fixtured FERROMIL® Media #NA (Pureplastic (polyester resin) without any abrasive particles) contacts theouter ring. The plastic media was shaped to the contour of the ring toprovide adequate surface contact. The Falex supplied 0-150 foot-poundSears Craftsman torque wrench with gravity acting on it is the only loadapplied to the traditional mechanical process. The ring is partiallysubmerged in 1% by volume REM® FBC-50 that is flowing through thereservoir at 6.5 milliliter/minute. See FIG. 2 for image of testapparatus.

[0048] The test ring is cleaned, dried and weighed before and afterprocessing on an analytical balance to determine metal removal.

[0049] The test ring has a weight of 22.3125 grams before processing.After a period of 3.0 hours at 460 RPM the weight is 22.3120 grams. Thisis a loss of 0.0005 grams total or 0.00017 grams per hour. Calculationsshow this to be a 0.9 μin. per hour change in dimension.

[0050] This example shows that an insignificant amount of metal isremoved by the non-abrasive plastic on a hardened steel surface when noactive chemistry is used.

EXAMPLE 5 Chemical Mechanical Machining with Non-Abrasive Plastic Tool

[0051] A Falex Corporation FLC Lubricity Test Ring, SAE 4620 steel, HRC58-63, (part #S-25), is finished using FERROMIL® VII Aero-700.

[0052] A Falex Corporation FLC Lubricity Tester is used to rotate thering at a set RPM while a piece of fixtured FERROMIL® Media #NA (Pureplastic (polyester resin) without any abrasive particles) contacts theouter ring. The plastic media was shaped to the contour of the ring toprovide adequate surface contact. The Falex supplied 0-150 foot-poundSears Craftsman torque wrench with gravity acting on it is the only loadapplied to the chemical mechanical machining process. The ring ispartially submerged in FERROMIL® VII Aero-700 at 12.5% by volume that isflowing through the reservoir at 6.5 milliliter/minute. See FIG. 2 forimage of test apparatus.

[0053] The test ring is cleaned, dried and weighed before and afterprocessing on an analytical balance to determine metal removal.

[0054] The test ring has a weight of 22.1059 grams before processing.After a period of 3.0 hours at 460 RPM the weight is 22.0808 grams. Thisis a loss of 0.0251 grams total or 0.00837 grams per hour. Calculationsshow this to be a 44.0 μin. per hour change in dimension. Thistranslates too more than 49 times the metal removal of Example 4 usingnon-abrasive tooling that is softer than the basis metal, and, thus, notcapable of exceeding plastic deformation, shear strength or tensilestrength of the basis metal.

[0055] Examples 4 and 5 demonstrate that significant amounts of metalcan be removed from hardened steel even using a non-abrasive plastic. Atool fashioned from plastic then can be used to shape and/or size and/orsurface finish a hardened steel surface when active chemistry is used.It is reasonable then that tools fashioned from harder materials willhave greatly extended lives because they do not have to exert highforces or experience high localized temperatures. The tool will lastlonger since it can remove metal by exerting only the force needed toremove the soft conversion coating.

[0056] In addition, these two examples show that metal removal from veryhard surfaces can be done with smaller machines than those used inconventional machining since less force needs to be exerted. The minimalstructural deflections and lower temperatures under the reduced toolpressure, especially on delicate workpieces, will minimize and/oreliminate structural distortion and increase machining accuracy andprecision. Since the metal removal rate is 44.0 μin. per hour, it isapparent that the machining can have an extremely high resolution ofremoving metal in increments of 1.0 μin.

EXAMPLE 6 Chemical Mechanical Surface Finishing

[0057] The root fillet area of a gear tooth was chemically mechanicallysurface finished to remove the axial grind lines. A tool was created byusing a section of high-speed steel wire with a diameter of 0.067 in.wrapped with 600 grit wet/dry silicon carbide paper. The tool wasrotated at approximately 80 RPM. The tool was held against the rootfillet area of a gear tooth (Webster, AISI 8620 carburized steel,17-tooth gear, 8-diametral pitch and 25° pressure angle, fillet radiusof approximately 0.0469 inches) with very light pressure. A solution of60 g/L oxalic acid and 20 g/L sodium metanitrobenzene sulfonate wasintroduced to the contact surface drop-wise (1-2 drops per 10 seconds).This was done for a period of 15 minutes. The silicon carbide paper waschanged once after surface finishing for 10 minutes.

[0058] Examination of the surface finished workpiece at 10×magnification revealed that one or two axial grind lines remained withthe majority of the surface being line free, smooth and flat. This showsthat surface finishing can be executed on critical recessed surfacesusing chemical mechanical surface finishing while maintaining very tightdimensional tolerances. Furthermore, machine and/or grind lines on theroot fillet regions of gears can be removed by a relatively simplechemical mechanical surface finishing. Any lines created by using alight abrasive tool will be orthogonal to the axial grind lines.Therefore, tooth bending fatigue will be reduced significantly extendingthe gear's life.

[0059] The present invention is not limited to gears, but can be appliedto any hard metal surface that experiences dynamic fatigue. The abilityto shape and surface finish in one step will increase the manufacturingefficiency of a variety of workpieces.

[0060] While the apparatuses and methods of this invention have beendescribed in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to the processdescribed herein without departing from the concept and scope of theinvention. All such similar substitutes and modifications apparent tothose skilled in the art are deemed to be within the scope and conceptof the invention as it is set out in the following claims.

What is claimed is:
 1. A process comprising: a. providing a tool; b.introducing an active chemistry onto a workpiece, the active chemistrybeing capable of reacting with the workpiece to form a conversioncoating on the workpiece, the conversion coating being insoluble in theactive chemistry such that the conversion coating protects the workpiecefrom further reaction; and c. contacting the tool with the workpiecewith a relative motion therebetween, until a desired surface property ofthe workpiece is reached; wherein the contact between the tool and theworkpiece removes the conversion coating from the workpiece, therebyexposing the workpiece to further reaction with the active chemistrysuch that the conversion coating is allowed to reform on the workpiece.2. The process of claim 1 wherein the surface property of the workpieceis selected from the group consisting of surface finishing, shaping,sizing and combinations thereof.
 3. The process of claim 1 wherein theactive chemistry is water-based or organic-based.
 4. The process ofclaim 1 wherein the active chemistry comprises active ingredientsselected from the group consisting of phosphate salts, phosphoric acid,oxalate salts, oxalic acid, sulfamate salts, sulfamic acid, sulfatesalts, sulfuric acid, chromates or chromic acid, and mixtures thereof.5. The process of claim 1 wherein the active chemistry is a concentratedacid.
 6. The process of claim 5 wherein the concentrated acid issulfuric acid, methane sulfonic acid or phosphoric acid
 7. The processof claim 1 wherein the active chemistry comprises activators oraccelerators selected from the group consisting of selenium, zinc,copper, manganese, magnesium and iron phosphates.
 8. The process ofclaim 1 wherein the active chemistry comprises inorganic or organicoxidizers selected from the group consisting of persulfates, peroxides,meta-nitrobenzenes, chlorates, chlorites, nitrates and nitrites andcompounds thereof.
 9. The process of claim 1 wherein the activechemistry is introduced onto the workpiece with a diluent or adispersant.
 10. The process of claim 9 wherein the diluent or dispersantis selected from the group consisting of water, organic liquids,paraffinic oils, silicone oils, synthetic oils, other oils, lubricants,greases, and combinations thereof.
 11. The process of claim 1 whereinthe workpiece is formed from a metal.
 12. The process of claim 11wherein the conversion coating comprises a compound selected from thegroup consisting of an oxide of the metal, a phosphate of the metal, anoxalate of the metal, a sulfate of the metal, a sulfamate of the metal,and a chromate of the metal.
 13. The process of claim 11 wherein themetal is selected from the group consisting of iron, titanium, nickel,chromium, cobalt, tungsten, uranium and alloys thereof.
 14. The processof claim1 wherein the relative motion between the workpiece and the toolis caused by moving the tool across the workpiece, wherein the workpieceis stationary.
 15. The process of claim1 wherein the relative motionbetween the workpiece and the tool is caused by moving the workpieceacross the tool, wherein the tool is stationary.
 16. The process ofclaim1 wherein the relative motion between the workpiece and the tool iscaused by simultaneous movement of both the tool and the workpiece,wherein neither the tool nor the workpiece is stationary.
 17. Theprocess of claim 1 wherein the tool is non-abrasive.
 18. The process ofclaim 1 wherein the tool is low abrasive.
 19. The process of claim 1wherein the tool is rigid.
 20. The process of claim 1 wherein the toolis flexible such that it conforms to the workpiece.
 21. The process ofclaim 1 wherein the tool is a mating surface of the workpiece or afacsimile thereof.
 22. The process of claim 21 wherein the tool isformed from a non-reactive material, such that a conversion coating isnot formed on the tool.
 23. The process of claim 22 wherein thenon-reactive material is selected from the group consisting of wood,paper, cloth, ceramic, plastic, polymer, elastomer, and metal.
 24. Theprocess of claim 21 wherein the tool is reactive to the active chemistrysuch that a second conversion coating is formed on the tool.
 25. Theprocess of claim 24, further comprising continuing the process until adesired surface property of the tool is reached.
 26. The process ofclaim 25 wherein the surface property of the tool is selected from thegroup consisting of surface finishing, shaping, sizing and combinationsthereof.
 27. The process of claim 1 wherein the workpiece comprises theroot fillet of a gear, wherein the tool removes surface deformities fromthe root fillet of the gear, wherein the surface deformities areselected from the group consisting of machine lines, grind lines, shotpeening patterns and combinations thereof.
 28. The process of claim 1wherein the workpiece comprises a gear and the tool comprises a matinggear or facsimile thereof.
 29. The process of claim 28 wherein the toolis reactive to the active chemistry such that a second conversioncoating is formed on the tool.
 30. The process of claim 29, furthercomprising continuing the process until a desired surface property ofthe tool is reached.
 31. The process of claim 30 wherein the surfaceproperty of the tool is selected from the group consisting of surfacefinishing, shaping, sizing and combinations thereof.
 32. The process ofclaim 1 wherein the workpiece comprises a bearing race and the toolcomprises a plurality of mating bearing balls or rollers or facsimilesthereof.
 33. The process of claim 32 wherein the tool is reactive to theactive chemistry such that a second conversion coating is formed on thetool.
 34. The process of claim 33, further comprising continuing theprocess until a desired surface property of the tool is reached.
 35. Theprocess of claim 34 wherein the surface property of the tool is selectedfrom the group consisting of surface finishing, shaping, sizing andcombinations thereof.
 36. The process of claim 1 wherein the workpieceand the tool are assembled in a housing.
 37. The process of claim 1carried out at a temperature less than the thermal degradationtemperature of the workpiece.
 38. The process of claim 1 wherein thetool is non-abrasive and is contacted with the workpiece at a force lessthan the plastic deformation of the workpiece.
 39. The process of claim1 wherein the tool is non-abrasive and is contacted with the workpieceat a force less than the shear strength of the workpiece.
 40. Theprocess of claim 1 wherein the tool is non-abrasive and is contactedwith the workpiece at a force less than the tensile strength of theworkpiece.
 41. The process of claim 1 wherein the contact between thetool and the workpiece causes material to be removed from the workpieceat a theoretical resolution of 1.0 microinch.
 42. A process comprising:a. providing a first mating gear; b. introducing an active chemistryonto the first mating gear, the active chemistry being capable ofreacting with the first mating gear to form a first conversion coatingon the first mating gear, the first conversion coating being insolublein the active chemistry such that the first conversion coating protectsthe first mating gear from further reaction; c. providing a secondmating gear, wherein the active chemistry is capable of reacting withthe second mating gear to form a second conversion coating on the secondmating gear, the second conversion coating being insoluble in the activechemistry such that the second conversion coating protects the secondmating gear from further reaction; and d. contacting the first matinggear with the second mating gear with a relative motion therebetween,until a desired surface property of both the first mating gear and thesecond mating gear is reached; wherein the contact between the firstmating gear and the second mating gear simultaneously removes the firstand second conversion coatings from the first and second mating gears,respectively, thereby exposing the first and second mating gears tofurther reaction with the active chemistry such that the first andsecond conversion coatings are allowed to reform on the first and secondmating gears, respectively.
 43. The process of claim 42 wherein thesurface property of both the first mating gear and the second matinggear is selected from the group consisting of surface finishing,shaping, sizing and combinations thereof.
 44. The process of claim 42wherein the first mating gear and the second mating gear are locatedwithin a transmission or gearbox, wherein the contact between the firstmating gear and the second mating gear occurs during operation of thetransmission or gearbox.
 45. A process comprising: a. providing a matingbearing race; b. introducing an active chemistry onto the mating bearingrace, the active chemistry being capable of reacting with the matingbearing race to form a first conversion coating on the mating bearingrace, the first conversion coating being insoluble in the activechemistry such that the first conversion coating protects the matingbearing race from further reaction; c. providing a plurality of matingrolling elements, the active chemistry being capable of reacting withthe mating rolling elements to form a second conversion coating of themating rolling elements, the second conversion coating being insolublein the active chemistry such that the second conversion coating protectsthe mating rolling elements from further reaction; and d. contacting themating bearing race with the plurality of mating rolling elements with arelative motion therebetween, until a desired surface property of boththe mating bearing race and the mating rolling elements is reached;wherein the contact between the mating bearing race with the pluralityof mating rolling elements simultaneously removes the first and secondconversion coatings from the mating bearing race and the plurality ofmating rolling elements, respectively, thereby exposing the matingbearing race and the plurality of mating rolling elements to furtherreaction with the active chemistry such that the first and secondconversion coatings are allowed to reform on the mating bearing race andthe plurality of mating rolling elements, respectively.
 46. The processof claim 45 wherein the surface property of both the mating bearing raceand the mating plurality of mating rolling elements is selected from thegroup consisting of surface finishing, shaping, sizing and combinationsthereof.